This invention relates to a circuit for transmitting energy to and from coils, or for transmitting the energy stored in a coil to another coil through a capacitor.
FIG. 1 illustrates a circuit of this type, as disclosed in copending U.S. application Ser. No. 473,408, entitled, "Apparatus for Transmitting Energy To and From Coils" filed, Mar. 9, 1983, commonly assigned, the disclosure of which is hereby incorporated by reference. In FIG. 1, there is shown a circuit comprising a capacitor 1 used in single polarity, diodes 21, 22, a coil 31 for releasing energy, a coil 41 for absorbing energy, self-controllable on-off switches 51, 52, a circuit 81 for controlling the flow rate of the current to control the on-off operation of the switch 51 to make the voltage of the capacitor 1 constant, and a circuit 82 for controlling the flow rate of the current by turning on and off the switch 52.
The operation of the circuit shown in FIG. 1 will now be described. FIGS. 2(1)-2(4) show the operating modes of the switches 51, 52 and the directions of the current flowing in the circuit making it clear that there are four kinds of operating modes. FIGS. 3(a)-(e) illustrate an example of the waveform of each component when .DELTA.t is set as a time controlling interval. FIGS. 3(a)-(e) show the voltage Vc across the terminals of the capacitor 1, the waveform i.sub.D21 of the current drawn by the diode 21, the voltage V1 across the terminals of the coil 31, the waveform i.sub.S52 of the current drawn by the switch 52, and voltage V2 across the terminals of the coil 41, respectively.
In FIG. 1, the switch 51 is controlled in such a way that the flow rate of the current therein is regulated by the control circuit 81 to make the voltage across the terminals of the capacitor 1 constant and such that it is turned on and off at preset time intervals. On the other hand, the flow rate of the current directed into the switch 52 is regulated by the control circuit 82 so that it is turned on and off at preset time intervals and operates to control the voltage applied to the coil 41 according to the quantity of the energy transmitted to the coil 41.
Since the circuit shown in FIG. 1 is constructed as above, it has disadvantages such that the transmission of energy between coils is unidirectional and such that, when a coil with less energy loss, including a supercondutive coil or the like, is used as a load, energy must be consumed by an energy releasing circuit (not shown) each time the operation of the coil 41 is terminated; the problem is that the direction of the current flowing through the coil is unidirectional only.